Nothing gained by training writer (3)
I believe the answer is:
poe
'writer' is the definition.
(Edgar Allan Poe)
'nothing gained by training' is the wordplay.
I cannot really see how this works, but
'nothing' could be 'o' (looks like zero - 0) and 'o' is found in the answer.
'training' could be 'pe' and 'pe' is present in the remaining letters.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for poe that I've seen before include "American short story writer" , "Edgar Allan ..., American writer of the macabre" , "Edgar Allan . . ., American writer of creepy stories" , "The Raven writer" , "Short-story writer" .)